Depth gauge



Aug. 6, 1940. c. HA ALLEN ET AL DEPTH GAUGE Filed July 29, 1958 NIH-u Patented Aug. 6, 1940 DEPTH GAUGE Charles H. Allen and Rosslyn C. Allen, Pittsburgh, Pa.

Application July 29, 1938, Serial No. 222,011

3 Claims.

This invention relates to a gauge, andwhile primarily designed and intended for ascertaining and indicating variations in the depths, from required standards, of internal screw threads, in sleeve couplings for pipes and the like, it will be obvious that the device may be employed for Vany other purposes rwherein it is found to be applicable.

important objects and advantages oi the invention are to provide an appliance of the character described, which is operable for accurately and quickly measuring and indicating variations from the proper depths of internally disposed screw threads, which may be. readily and conveniently engaged on the product to be measured or removed from the latter, which is simple in its construction and arrangement, positive in itsy action, attractive in appearance, durable and efficient in its use, and economical in its manufacture.

With the foregoing and other objects in View which will appear as the description proceeds, the invention resides in the novel construction, combination and arrangement of parts therein specically described and illustrated in the accompanying drawing, but it is to be understood that the latter is merely illustrative of an embodiment of the invention, and that the actual needs of practice and manufacture may require certain mechanical variations iro-m the embodiment shown. It is, therefore, not intended to limit the invention to the disclosure thereof illustrated, but rather to dene such limitations to thev scope of the claims hereunto appended.

ln the drawing wherein like numerals of reference designate corresponding parts throughout the several views:

Figures 1 and 2 are, respectively, side elevational and top plan views of a depth gauge coni structed in accordance with the invention.

Figure 3 is a longitudinal cross sectional View of the barrel and ofl associated parts.

Figure 4 is a top plan view of the balance beam. Figure 5 is a rear end view of the clamping arm and of attached bell crank lever.

`Figure 6 is a front end View of the gauge applied to the work to be measured.

Figure '7 isI an enlarged side view of the seatin plate, and Figure 8 is an enlarged fragmentary side view of the balance beam and of its fulcrum suspension elements. i

Referring in detail I denotes an elongated, tubular and cylindrical body or barrel, which is disposed horizontally and has its respective ends i closed by a pair of closure plugs 2.

An elongated balance beam .i is mounted in the barrel l, and has an accurately equi-poised fulcrum suspension in the latter, allowing the beam to alternately move up and down in a limited see-saw movement.r The fulcrum suspension or axis of the beam comprises a sphere or ball i which is' shiftably mounted in an vaperture provided therefor in said beam centrally of the ends of the latter. The ball is pro-vided withl a transversely extending bore 5, which latter is '10 formed with a corresponding disposed, triangularly-shaped groove li in the top wall thereof. A fulcrurn pin l is removably and transversely iixed, as at 8, in the barrel and extends through the bore of the ball. The fulcrum pin has a knife- 15 Yedge top edge S seating in the apex of the triangularly-shaped bore groove il. The bottom of the ball 4 is provided with a groove l@ extending parallel to the bore groove 6. A. set screw I I is adjustably mounted in the beam 3 and eni'20 gages in the ball groovey Ill. The set screw maintains the ball 4 in the beam in a position disposing the apex of the groove 5 upwardly at all times, but otherwise allows the automatic adjustment of said ball in the beam to an extent, whereby the 125 top edge 9 of the fulcrum pin l will accurately seat in the apex of the bore groove l throughout the length thereof. This fulcrum suspension of the beam 3 provides an axis for the latter with only a minimum of friction.

The balance beam 3 has its bottom face tapered from its center toward respective ends thereof to conserve weight, and has a forked front end l2 which is beveled to provide comparatively sharp top edges I3. The top rear portion le, of the B5 balance beam, is `iiat and recessed to dispose same below theplane of the top of said beam` An anvil I5, having tapered sides and a rounded top l@ extending parallel to the longitudinal disposition of the barrel l, is secured to the top a0 of the latter at the front end thereof. The anvil is provided with a vertical passage ll, communicating with the interior of the barrel, for receiving a vertically disposed plunger i8. The upper end of the latter carries a tip IS, which is pointed, and has a fixed, detachable connection with said plunger, and projects through the top of the passage ll.

The plunger I8 projects through the forked front end Ii of the balance beam 3, and is carried by a cross-pin 2t, which is xed in said plunger and seats upon the sharp top edges i3 of said forked front end. The plunger is vertically shiftable and free of friction in the anvil passage Il, and is held against rotation in the latter by a pin 2| xed in the plunger and projecting rearwardly in the forked beam end I2. The lower end of the plunger I8 has a frictionless engagement in a socket bearing 22 fixed in the bottom of the barrel I.

A dial indicator 23, of any suitable conventional construction, is mounted on a support 24, which latter is fixed to the top of the barrel I at the rear end thereof. The indicator is provided with a scale graduated dial, each graduation representing one one-thousandth of an inch, and includes a spring controlled actuating rod 25.

'Ihe latter extends vertically through a passage,

provided therefor in the support 24 and projects into the barrel and has its lower end seated upon the flat, recessed rear end I4 of the balance beam `3. The normal action of the spring controlled actuating rod 25 will shift the balance beam 3 to move the plunger I 8 vertically upward in the anvil passage I'I. The depression of the plunger, however, will shift the balance bean to move the actuating rod upwardly whereby the indicator is' operated to indicate, upon the dial of the indicator the extent of such depression of the plunger.

A clamping arm 23 is provided for properly engaging the product or work to be measured. 'Ihe rear end of the clamping arm is detachably iixed to the top of the upwardly disposed connecting member 2l of a bell crank lever 28 by means of a bolt 29 having a knurled head 3Il. The bell crank lever is pvotally connected by a pivot pin 3l in a bearing bracket 32, which latter is fixed on the top of the barrel I adjacent to the indicator 23.

The clamping arm 26 is of considerable length and extends forwardly to the anvil I above the barrel I from its connection with the bell crank lever 28. The front free end of the clamping arm is provided with an integrally formed crosshead 33. The latter has a longitudinal concavely curved bottom face 34, which is provided with an aperture 35 for normally receiving and protecting the pointed plunger tip I9 when the instrument is not in use.

The bell crank lever 28 includes a rearwardly disposed depression member 36 adapted to be engaged and depressed by the thumb of the operator for elevating or spacing the cross-head 32 from the anvil I5 when the product to be measured is to be placed between said cross-head and anvil. A spring 31 is mounted on the bearing bracket 32 and engages the depression member 33, of the bell crank lever. The normal action of the spring 31 actuates the bell crank lever to force the cross-head 33 toward the anvil I5. The cross-head 33 cannot actually contact with the anvil I5, as the movement of the bell crank lever, to lower said cross-head, is limited by the engagement of the toe 45, of the bell crank lever, with the bearing bracket 32, as shown in Figure 1.

To assure the proper alignment of the connection of the clamping arm 2S, with the bell crank member 2l, the top face of the latter is provided with a triangularly shaped rib 38 which is engaged by a correspondingly shaped groove 33 formed in the bottom face of the clamping arm at the rear end of the latter.

A seating plate 43, suitably apertured for the passage of the bolt 29, is mounted between the head 30 of the latter and the top face of the clamping arm 26. The seating plate carries a pair of fixed, depending guide pins 4I, which extend into pockets provided therefor in the top of the clamping arm. Each of the guide pins is surrounded by a spring 42, which are mounted in respective pockets and which normally function to force the seating plate upwardly toward the bolt head 30.

The function of the seating plate 40 is to resiliently sustain the clamping arm 25, when the bolt 29 is partially released from its engagement in the lever member 21. When the bolt 29 is so released the clamping arm may be lifted against the action of the springs 42 to cause the arm groove 39 to clear the rib 38, and thereby allow the clamping arm to be swung laterally to shift the cross-head 33 from above the anvil I5 to provide the necessary clearance for Calibrating the instrument or for any other purposes required. Further, when returning the clamping arm to its normal, operative position, the action The concaved bottom face 34, of the cross-head,

conforms to the engaged curvature of the coupling and snugly seats upon the latter. Such engagement of the coupling will be maintained by the resilient action imparted to the clamping arm 26 by the spring 31. The plunger tip I9 enters a depression between a pair of adjacent convolutions of the screw thread, and if the said depression is precisely of the proper depth, the balance beam 3 will be actuated to operate the indicator to register Zero, thereby showing that the screw thread is of the proper depth. However, should the screw threads be too deep or too shallow the balance beam will be actuated to operate the indicator to register the variation of the thread screw depth from the proper depth.

The indicator 23 is s o calibrated that when a screw thread of proper depth is placed on the anvil I5 and engaged by the plunger tip I9, in the manner stated, the balance beam 3 will be actuated to operate the indicator to register zero, and variations from the proper depth will be registered, respectively as minus or plus from zero as such variation may be, by graduation representing one one-thousandth of yan inch.

'I'he present invention provides a most eicient instrument of its kind, which may be readily employed by a person of ordinary skill, for precisely measuring screw thread depth variations, even if the latter be so iniinitesimal as to be incalculable by any other device used for analogous purposes.

What we claim is:

1. A depth gauge for internally disposed screw threads comprising a horizontally disposed tubular body, a balance beam pvotally connected intermediate of its ends in said body, an anvil provided with a vertically extending passage mounted on the top at the front end of said body, a plunger having a pointed tip mounted and vertically shiftable in said passage and supported on the front end of said beam, and an indicator element mounted on the top at the rear end of said body and engaged by the rear end of said beam and actuated by the movement of the latter for indicating the extent of the movement of said plunger, a clamping arm pvotally supported by said body, and means tending to force said arm toward said anvil.

2. A depth gauge for internally disposed screw threads comprising a horizontally disposed tubular body, a balance beam pivotally connected intermediate of its ends in said body, an anvil provided with a vertically extending passage mount- `ed on the top at the front end of said body, a

plunger having a pointed tip mounted and vertically shiftable in said passage and supported on the front end of said beam, and an indicator element mounted on the top at the rear end of Vsaid body and engaged by the rear vend of said beam and actuated by the movement of the latter for indicating the extent oi the movement of said plunger,` a clamping arm pivotally supported by said body, and spring controlled means carried by said body normally tending to force the free end of said arm toward said anvil.

20 3. A depth gauge for internally disposed screw threads comprising a horizontally disposed tubular body, a balance beam pivotally connected intermediate of its ends in said body, an anvil provided With a vertically extending passage mounted on the top at the front end of said body, a plunger having a pointed tip mounted and vertically shiftable in said passage and supported on the front end of said beam, an indicator element mounted on the top at the rear end of said body Aand engaged by the rear end of said beam l and actuated by the movement of the latter for indicating the extent of the movement of said plunger, a bearing bracket iXed on said body, a bell crank lever pivotally supported by said bracket, a clamping arm having one end thereof fixed to said lever, and a spring engaging said body and said lever and normally tending to force the free end of said arm toward said anvil.

l CHARLES I-I. ALLEN. ROSSLYN C. ALLEN. 

